Waiting crowds cheered as the boy, who has not been identified, was carried out on a stretcher.

His face was covered in dust, and medics placed an IV drip into his arm. A blue brace had been placed around his neck. He appeared stunned, and he blinked in the sunlight.

A USAID team had been working at the scene overnight to try to free the boy.

Andrew Olvera, head of the USAID disaster response team, said before the rescue that the boy had not been buried very deep, but that he was trapped between two collapsed floors of the building.

The survivor, named as Pemba Tamang, was said to be 18 years old.

LB Basnet, the police officer who crawled into a gap in the rubble to reach Pemba, said he was surprisingly responsive.

"He thanked me when I first approached him," said Mr Basnet.

"He told me his name, his address, and I gave him some water. I assured him we were near to him."

Rescuers eventually used jacks to lift the concrete slabs that had wedged him in, said Mr Basnet.

An American disaster response team had been helping the Nepalese.

"He's not too far down, but the floors have collapsed and he'd been pancaked between them," Andrew Olvera, who is heading the team from the US agency for international development, said shortly before the boy was freed.

Twisted ropes of steel reinforcing rods were all that stopped huge concrete slabs from falling onto the scene. Two concrete floors hung down in front of the building like curtains.

The rescue was a rare bit of good news in a city that has known little but despair since the earthquake hit on Saturday, leaving more than 5,500 people dead across this poverty-wracked Himalayan nation.

Asked how the survivor had lasted for so many days, Mr Basnet replied: "He survived by good faith."